Type "syslog | grep shutdown" into terminal and post the results. I've experienced this before on a 2012 rMBP and it turned out to be bad memory, which resulted in a logic board replacement. See if you can run MemTest86 to confirm.
I ended up cutting part of the antenna cable off from a broken display, stripping both cables, soldering them together, and covering them with some electrical tape. Not the cleanest solution, but definitely the cheapest!! Bluetooth and wifi fully work now.